Search

Numerous studies evaluating the effects of the incorporation of microalgae in feeds have reported favourable impacts on different physiological aspects of aquacultured fish. Although productivity is the major goal in terms of profitability in fish farming, however, qualitative aspects are gaining the attention of producers, given the relevance of quality attributes related to organoleptic parameters, proximal composition, and shelf life on the commercial value of fish. Indeed, microalgae are acknowledged for their richness in substances with potential positive effects on all those quality attributes. In this context, this study assesses the effects of finishing diets enriched with the microalga Nannochloropsis gaditana, either crude or enzymatically hydrolysed, on several quality parameters of gilthead seabream (Sparus aurata) fillets. Two inclusion levels (2.5 and 5%) of raw and enzymatically hydrolysed microalgal biomass were incorporated into diets, plus a microalgae-free control diet, and a 42-d feeding trial was carried out on fish of commercial size (approx. 500 g body weight). The influence of the experimental diets on fish biometry, fillet quality parameters, and shelf life was evaluated. The results indicate, overall, that microalgae-enriched diets yielded favourable, dose-dependent effects on several objective quality parameters of fillets, namely, improved fatty acid profile, reduced microbial counts, enhanced lipid oxidative status, and improved textural and skin colour attributes. Although the enzymatic pre-treatment of the microalgal biomass was expected to impact positively its functional effects on all quality parameters, however, no general trend was observed.

The aim of this work was to evaluate the effects of the dietary inclusion of Arthrospira sp. enzyme hydrolysate on gilthead seabream (Sparus aurata) juveniles in a 128-day feeding trial. Algal hydrolysate was tested at low inclusion level, namely, 2 and 4%, against a control diet without Arthrospira sp. supplementation. At the end of the feeding trial, fish body weight was recorded for growth evaluation. No significant differences were found among the experimental groups regarding growth performance or nutrient utilization, despite the fact that those animals fed with diets enriched with Arthrospira displayed higher trypsin, chymotrypsin, and leucine aminopeptidase enzyme activities, compared to fish fed with control diet. The ultrastructural study of the intestinal mucosa also revealed increased microvilli length and absorptive capacity in fish fed with Arthrospira sp. diets, especially at 4% inclusion level. Arthrospira supplementation was also responsible for lower lipid oxidation in muscle tissue, as well as for remarkable colour differences in skin, compared to control animals. These results suggest, overall, that low dietary supplementation with this microalgal hydrolysate might improve not only the intestinal ultrastructure and functionality but also muscle pigmentation and antioxidant capacity of juvenile gilthead seabream.

This study evaluates the potential of different algae extracts (Crassiphycus corneus, Cc, Ulva ohnoi, Uo, Arthrospira platensis, Ap, Haematococcus pluvialis, Hp) as additives for the preservation of rainbow trout fillets. The extracts were prepared with different water to ethanol ratios from the four algae species. The highest ferric reducing antioxidant power (FRAP) was observed in Uo extracted in 80% ethanol. Ap aqueous extract also had considerable FRAP activity, in agreement with a high total phenolic content. Radical scavenging activity (DPPH) was higher in Cc 80% ethanol extract, in agreement with a high total carotenoid content. In fact, when the algae aqueous extracts were assayed on the fish fillets, their antioxidant activity exceeded that of ascorbic acid (ASC). All algae extracts delayed microbial growth and lipid oxidation processes in trout fillets throughout the cold storage period compared to controls, and also improved textural parameters, these effects being more evident for Ap and Hp. With respect to the color parameters, the Hp extract prevented the a* values (redness) from decreasing throughout cold storage, a key point when it comes to colored species, not least salmonids. On the other hand, the Ap extract was not as effective as the rest of treatments in avoiding a* and b* decrease throughout the storage period, and thereby the color parameters were impaired. The results obtained, together with the natural origin and the viability for large-scale cultivation, make algae extracts interesting fish preservative agents for the food industry.

This work evaluates the effects of the dietary inclusion of crude or hydrolysed Arthrospira platensis (Cyanobac- teria) biomass on growth, muscle composition, digestive functionality and immune activities in gilthead seab- ream (Sparus aurata) fry (20.32 mg mean body weight). A 40-day feeding trial was conducted, aimed at assessing four experimental diets that included 5 or 10% (w/w) A. platensis, either crude or hydrolysed, plus a microalgae- free diet as control batch. Overall, none of the dietary treatments caused negative impacts on fish growth, body composition, muscle fatty acid profile, or innate immune response. Thus, the dietary inclusion of both crude and hydrolysed A. platensis reduced significantly the oxidation of muscle lipids, especially when using hydrolysed biomass, regardless of the dietary inclusion level. In relation to digestive enzymes, significantly higher levels of trypsin, chymotrypsin and leucine aminopeptidase activities were measured in fish fed on A. platensis-supple- mented diets compared to control fish. In addition, within each inclusion level (5 or 10% w/w), those animals fed with diets that included the hydrolysed biomass yielded consistently higher digestive enzyme activities than those receiving the crude biomass. Microalgae dietary inclusion also induced favourable changes in fish gut morphology, according to the increase in microvilli length and diameter observed. This fact might well have contributed to reinforce the role of the intestinal mucosa as a protective barrier against microorganisms, as well as to enhance the absorptive capacity of the intestinal mucosa. Finally, 10% inclusion of microalgae hydrolysate enhanced lysozyme activity in liver, this fact suggesting improved protection against infectious diseases. In conclusion, the positive effects observed in fish fed with the diets including A. platensis up to 10% (not least the hydrolysed biomass) with regard to the different parameters assessed (digestive enzyme activities, intestinal epithelium ultrastructure, muscle lipid oxidation, and lysozyme activity) suggest the benefits of including this product in starter feeds for gilthead seabream fry., Evaluación de los efectos de las microalgas, incluidas en dietas de dorada, sobre el crecimiento, supervivencia y resistencia a infecciones., ALGAFISH, SI

A 90-d feeding trial was conducted in which five groups of gilthead seabream (11.96 g initial body weight) were fed with a microalgae-free diet (control group, C) or four diets containing the microalgae Nannochloropsis gaditana at two inclusion levels (2.5% or 5%), either raw (R2.5 and R5 batches) or cellulose-hydrolyzed (H2.5 and H5 batches), to study their effect on the body and muscle growth. At 40 days, the highest values of body length and weight were reached in R5 group, but at 64 and 90 days, these were reached in R2.5. However, feed conversion rate, specific growth, daily intake, and survival (100%) were similar in all the groups. The acquisition of a discoid body shape was accelerated depending on the inclusion level of N. gaditana in the diets. Moreover, H5 diet affected the fish geometric morphology compared to R5 diet. The white muscle transverse area was similar in all groups at 40 days, with the exception of H2.5 group, which showed the lowest area. At day 90, C and R2.5 displayed the highest muscle growth, attributable to increased hyperplasia in C, and higher hypertrophy in R2.5. However, the highest proportion of small and medium fibers was observed in R5 and H5, ALGAFISH, Evaluación de los efectos de las microalgas, incluidas en dietas de dorada, sobre el crecimiento, supervivencia y resistencia a infecciones., SI

Macroalgae are a promising source of a vast variety of bioactive compounds with potential interest in aquaculture. In addition to their sustainable and renewable nature, numerous evidences have been reported pointing to positive effects on fish growth, nutrient utilization, and disease resistance. Nevertheless, the effects on fish quality objective parameters have been scarcely explored. In this study we assessed the influence of Ulva ohnoi included at low level (5%) in a diet for Senegalese sole (Solea senegalensis) on several quality attributes of fish (proximate analysis, texture profile analysis, lipid oxidation, fatty acid profile, pH, water holding capacity, and colour parameters). A 270-d feeding trial was carried out, in which juvenile animals were fed with an Ulva-enriched diet only for 90 d out of the total 270-d study. This enabled to evaluate whether the possible effects on fish were transitory or persistent at the end of the assay. Besides modest effects on fish growth at early stages, the differences attributable to Ulva supplementation were mostly focused on the lipid fraction, texture, and colour parameters. Thus, Ulva diet reduced muscle total lipid content and favoured muscle selective retention of n-3 polyunsaturated fatty acids (PUFA), not least eicosapentaenoic acid (EPA) and docosahexaenoic (DHA) acid, and also diminished lipid oxidation, especially after a period of frozen storage. In terms of consumers' acceptability, seaweed supplementation impacted favourably on fillet texture and colour attributes, namely by increasing lightness (L*) and yellowness (b*), whilst reducing redness (a*). These results are particularly remarkable taking into account that low inclusion level was considered (5%), and above all, that Ulva supplementation was interrupted after 90 d, but the effects mentioned persisted at least up to 270 d. These deferred long-term effects might well be of practical interest when it comes to modifying quality attributes of edible fish.

The combined effect of farm management practices, transport time, and ageing time on the electrophoretic changes of sarcoplasmic (SPP) and myofibrillar (MFP) protein fractions of goat kids was studied. A total of 64 suckling goat kids were withdrawn from two farms with &ldquo, high&rdquo, (GW) and &ldquo, low&rdquo, (DW) welfare-friendly management practices, and they were transported for 2 or 6 h immediately before slaughtering. Longissimus lumborum samples were obtained at 3, 8, and 21 days post-mortem, and muscle proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis SDS-PAGE. Both protein extracts displayed significant changes attributable to meat maturation. Managing conditions of kids in DW farms increased the post-mortem susceptibility of muscle proteins. Some MFP of Longissimus lumborum muscle, such as troponin T, as well as 26&ndash, 30 and 35&ndash, 37 kDa fractions were influenced significantly by deficient on-farm management, and therefore, these protein fragments might be considered as indicators of low-welfare on-farm management in goat kids.

This piece of research evaluates the presence of protease inhibitors in the macroalga Ulva ohnoi and provides an initial overview of their mode of action. The ability of Ulva protease inhibitors to inhibit digestive proteases of three marine fish species, as well as their capacity to hamper the hydrolysis of a reference protein by those fish proteases, were assessed. In addition, thermal stability and the mode of inhibition on trypsin and chymotrypsin were also studied. Dose-response inhibition curves and in vitro protein hydrolysis assays revealed a noticeable inhibition of fish enzymes when Ulva concentration increased in the assay. The thermal treatment of Ulva reduced markedly the inhibitory effect on fish digestive protease. Finally, Lineweaver&ndash, Burk plots indicated that trypsin and chymotrypsin inhibition consisted of a mixed-type inhibition mechanism in which the inhibitory effect depends on Ulva concentration. Overall, the results confirmed the presence of protease inhibitors in Ulva, though heat treatment was enough for inactivating these compounds.

The aim of this work was to evaluate two functional feeds for the gilthead seabream, Sparus aurata, containing low inclusion of two microalgae-based products (LB-GREENboost, LBGb; and LB-GUThealth, LBGh). Fish (12–13 g) were fed for 13 weeks a control diet or one of the four diets supplemented with both products at 0.5% or 1%. LBGb and LBGh did not affect specific growth rate or survival, but increased feed efficiency by decreasing feed intake and enlarging the intestines. LBGb increased hepatosomatic index and reduced cortisol levels in plasma, while both products lowered plasma lactate. Extensive metabolite and metabolic enzyme profiling revealed that microalgae supplementations, especially 1% LBGh: (i) decrease plasma lactate and increase hepatic glycogen, (ii) reduce hepatic gluconeogenesis, (iii) enhance hepatic lipogenic activity and lipid secretion, (iv) led fish to double triglyceride content in muscle and to stimulate its lipid oxidative capacity, and (v) increase the content of monounsaturated fatty acids and the omega-3 alpha-linolenic acid in muscle. This study demonstrates that both microalgae-based products are suited to improve feed efficiency and orchestrate significant changes in the intermediary metabolism in gilthead seabream juveniles.

Microalgae are a source of diverse high-value compounds, such as carotenoids and fatty acids, which have a potential application in aquafeeds. Some microalgae species present complex cell wall structures, which make them poorly digestible, thus limiting their use as a feed ingredient. Consequently, applying extracted compounds to aquafeeds instead of using the whole algal biomass is advantageous as this is expected to increase the bioavailability of these nutrients. The aim of this study was to evaluate the effect of the dietary inclusion (2%) of two extracts obtained from the microalga Nannochloropsis gaditana (one composed of saponifiable lipids and the other of non-saponifiable lipids), alone or in combination, on growth, muscle composition, skin color and lipid oxidation in juvenile gilthead seabream, Sparus aurata, following a 39-day trial. Overall, the inclusion of 2% of the saponifiable lipid extract did not affect the growth performance but fish muscle presented a lower percentage of docosahexaenoic acid (DHA) and a higher eicosapentaenoic acid (EPA) than that of the fish fed the diets lacking this lipidic fraction. Despite no effect being observed in fish growth performance, the inclusion of 2% of the non-saponifiable lipid extract enhanced the carotenoid content of the fish muscle, which prevented lipid oxidation, and modulated the skin pigmentation towards a yellow-greenish color. The present study confirms the success of applying both high-value microalgae lipidic extracts, alone or in combination, as feed additives for practical diets in juvenile gilthead seabream.

Studies aimed to assess up to what extent farming and transport previous to slaughtering might affect physiology and meat quality in young goat kids are needed, with the ultimate purpose of promoting practices that minimize stress in these animals. In this regard the effects of on-farm management and transport duration on some physiological responses and meat quality parameters in goat kids were assessed. Two farms representing 'high' and 'low' welfare-friendly management practices were selected. In total, 32 suckling kids were withdrawn from each farm, transported by road for 2 or 6 h, and then slaughtered. Blood samples were collected both on-farm and in the slaughterhouse, and biochemistry, cell counts and haematocrit were determined. After slaughtering, carcass quality parameters were measured. Longissimus dorsi muscle was dissected and pH, colour parameters, water holding capacity and shear force were measured throughout 8-day ageing period. Results indicate that, regardless its duration, transport caused significant effects on some blood parameters suggesting stress in live animals, like glucose, cortisol or creatine kinase. Despite the marked stress status in animals, this condition was not decisively reflected on L. dorsi quality parameters, but some effects were observed regarding fat cover in carcasses and colour parameters. The results suggest that postmortem changes throughout ageing were more decisive in terms of meat quality than stressful management either on-farm or during transport.

This study assesses the potential of two tannins, tannic acid (TAN) and quebracho tannin (QUE), to preserve objective quality parameters of rainbow trout fillets throughout a 15-d cold storage period, applied either alone or combined with alginate coating. Untreated fillets (C), and a set of fillets treated with ascorbic acid (ASC) were also included. All the additives reduced microbial counts and lipid oxidation of fillets, being the effects of TAN and QUE at least comparable to those of ASC, the most widely used antioxidant for fresh fish. The results also indicate that alginate by itself reduced lipid oxidation at late stages of the storage period, and increased fillet lightness (L*) as well, but caused scarce effects on other parameters involved in fillet deterioration. However, alginate and additives applied together enhanced the effects of the additives alone, especially regarding microbial and lipid oxidative parameters, this enabling prolonged shelf life of fillets. These valuable properties of commercial tannins, together with their natural origin and large-scale availability, might well enable further applicability of these substances to fish fillets preservation, not least with regard to coloured species, such as rainbow trout.

Encapsulation efficiency of protein in alginate or a combination of alginate and chitosan hydrogels was studied with the aim of ascertaining the adequacy of these carriers to deliver exogenous protein to fish orally. Bovine serum albumin (BSA) was chosen as model protein, and sea bream (Sparus aurata L.) juveniles as in vivo fish model. A three step approach was followed, according to the next scheme: (i) evaluation of different encapsulation protocols in terms of their efficiency to retain BSA; (ii) assessment of the retaining capacity of capsules under in vitro systems, including those that simulate gastric and intestinal conditions, and (iii) in vivo assay, in which the fate of encapsulated BSA during its transit throughout the fish gut was assessed. The results indicate that a combination of alginate and chitosan polymers (30 g L−1 and 1 g L−1, respectively) yielded the best balance among encapsulation efficiency, BSA protection against gastrointestinal proteolytic enzymes, and further sustained release of protein in the gut lumen of gilthead sea bream.

The effects of freezing and freezing-thawing cycles during cold storage have been studied in meagre (Argyrosomus regius) fillets. Fillets were subjected to three conservation protocols: fresh, freezing at –20°C, and repeated freezing-thawing cycles. Fresh fillets were stored (4°C, 15 days), and the same protocol was followed for freezing and freezing-thawing after the freezing period. Freezing and freezing-thawing fillets were softer and presented lower water holding capacity than fresh, mostly attributable to collagen solubilization, and partial myofibrillar protein degradation. Cold storage (4°C) during 15 days caused softening in fresh and frozen fillets attributable to myofibrillar protein hydrolysis. Freezing-thawing cycles increased proteolysis, this leading to unacceptable softening even from early stages of further cold storage, and this was also revealed by SDS-PAGE.

The Senegalese sole, Solea senegalensis, is a flatfish with increasing interest in the European aquaculture. However, one of the main limitations found in this species is related to the scarce attraction to commercial aquafeeds, thus determining low feed intake in fish farms. The aim of this study was to evaluate four ingredients of marine origin (fish meal hydrolysate [FMH], polychaete meal [POM], mussel meal [MUM], and squid meal [SQM]) as potential attractants for juvenile Senegalese sole. Four experimental feeds containing 10% of the potential attractants, plus a control diet without these ingredients, were evaluated. A total of 150 fish were distributed into ten 40-L tanks (duplicate tanks per feed). A Latin square design was carried out, and hence all the experimental diets were offered to each tank in successive periods of 7d. Fish were fed twice a day (morning and afternoon), and the feeding behavior of the animals was assessed by direct observations. Behavioral pattern assessed was classified as distant orientation, near orientation, or continuation of intake. The acceptability index for each behavioral phase and experimental feeds used was established for each observation. No behavioral differences could be noticed between the morning and the afternoon feedings. FMH showed the greatest attractant potential than among the ingredients assessed, and consequently this ingredient yielded the higher feed intake rates. On the other hand, POM was not the best attractant for juvenile Senegalese sole. Marine aquaculture in southern European countries is mainly focused on few fish species, such as sea bream, Sparus aurata, and sea bass, Dicentrarchus labrax. Because of the high volume of production of these species, markets have begun to show saturation. The investigation of new species for aquaculture is a necessary strategy for the future with the aim of increasing farm profitability and expanding market opportunities (Dinis et al. 1999).

Senegalese sole is one of the most promising fish species cultivated in the Southern European countries. This study was aimed at assessing the effects of microalgae biomass added to diets for Senegalese sole juveniles on fish growing and condition status. Three isoproteic (52%) and isolipidic (10%) were formulated containing 15% Tisochrysis lutea (TISO), Nannochloropsis gaditana (NAN), or Scenedesmus almeriensis (SCE) biomass, respectively. An experimental microalgae-free diet (CT) and a commercial diet (COM) were used as controls. Fish were fed at 3% of their body weight for 85 days. Final body weight of fish fed microalgae-supplemented diets did not differ from group fed CT diet. Fish-fed CT, TISO, NAN, and SCE showed higher growth performance and nutrient utilization figures than specimen-fed COM diet. The highest carcass lipid content was found in COM group (141 g kg−1), and no differences were observed in body protein content. Ash was significantly higher in TISO, NAN, and SCE groups compared to fish-fed CT. Muscle EPA and DHA contents were not modified owing to the different dietary treatments. The n3/n6 and EPA/DHA ratios in muscle were similar in all the experimental groups. The quantification of digestive proteolytic activities did not differ among experimental groups, although differences in the protease pattern in digestive extracts by zymography were revealed in those fish fed on COM diet. Both α-amylase activity in the intestinal lumen and leucine aminopeptidase in the intestinal tissue were significantly lower in COM fish. Specimens fed on SCE diet showed a higher leucine aminopeptidase activity associated to the intestinal tissue compared to NAN-fed fish (0.40 and 0.25 U g tissue−1, respectively). The ultrastructural study revealed that the dietary inclusion of algal biomass, especially T. lutea and N. gaditana, had a positive impact on the absorptive capacity of the intestinal mucosa. The highest values for the parameters microvilli length and microvilli absorption surface were observed in fish fed on NAN diet (1.99 μm and 45.93 μm2, respectively). Even though further studies aimed at optimizing commercial formulas for Senegalese sole are required prior to any large-scale practical utilization, the results obtained clearly suggest the potential of microalgae as dietary ingredients for this fish species.

In the present study, the nutritional value of Tetraselmis suecica and Tisochrysis lutea (previously known as Isochrysis aff galbana T-ISO strain) freeze-dried biomass for feeding Sparus aurata fry was evaluated. A total of 25,500 fry (3.7 mg body weight) were fed for 55 days on diets containing 5 and 10%(w/w) Tetraselmis or Tisochrysis, as well as on a microalgae-free diet. Fish fed 5 % Tetraselmis showed higher growth performance, nutrient utilization, and survival values than fish fed Tisochrysis. The use of microalgae significantly decreased the body lipid content in fry fed the highest microalgae level. Fry fed Tisochrysis-supplemented diets increased the DHA content in muscle, and consequently the EPA/DHA ratio decreased significantly, whatever dietary level considered. In general, digestive protease activities were not adversely affected by dietary microalgae inclusion, although slight variations were observed during fish development. Microalgae utilization causes a positive effect on intestinal mucosa ultrastructure owing to an increase of total enterocyte absorption surface that was observed in fish fed microalgae-supplemented diets. Cluster analysis of data separated clearly fish fed Tisochrysis-supplemented diets from the rest of experimental groups. This study confirms that Tetraselmis freeze-dried biomass can be used as dietary ingredient in started feeds for S. aurata fry, although an inclusion level of 5 % is recommended., SI

A sensitive and quick method was developed to determine the presence of α-amylase in the gut of aquatic organisms, as well as its sensitivity to inhibitors. The assay is based on the utilization of Petri dishes filled with starch–agarose gel as a substrate for the enzyme solution, which is placed in small wells punched in the surface. Circular zones produced by the action of amylase remain colourless after staining with lugol. Pure commercial porcine amylase was used to fit the better conditions for developing the assay (1 g L–1 starch in the gels, 4 h of incubation). The diameter of the cleared zones were related to the activity of enzyme and the method detected linearly amylase activity in a range of 2–20 U well–1, so it was used to reveal the presence of amylase in digestive extracts obtained from different sparid fish. The method was also used to evaluate the effect produced by a specific inhibitor on fish amylases, showing a linear response when the ratio inhibitor:enzyme (in units) changed from 20:1 to 2:1. Comparison of the cleared zones produced by amylases of sparid fish in the presence or absence of inhibitor, revealed differences in their sensitivity to inhibition, which ranged from 15 to 50% of total activity. The assay is proposed for a preliminary evaluation of possible inhibitors contained in feedstuffs used in fish feeding.

The presence of digestive carbohydrases was determined in seabream intestines, and the main activity identified was amylase. Optimum activity for this enzyme was found at pH 8.0 at 40 °C. Amylase activity was highly sensitive to extreme pH, and temperatures exceeding 50 °C. The use of SDS–PAGE zymograms allowed identification of amylase in the form of a high molecular mass fraction exceeding 100 kDa. Results confirm the existence of a well developed amylase equipment in this species which supports the possibility of increasing the amount of carbohydrates in the formulation of its commercial feeds.

The aim of this study was to assess the potential effects of replacing part of the dietary protein by lipid or carbohydrate on the characteristics of dentex muscle. Dentex were hand-feed four isoenergetic diets (22.6 MJ kg − 1 gross energy) with protein:lipid:carbohydrate ratios 43/16/28 (D1); 43/24/4 (D2); 38/19/28 (D3), and 38/24/13 (D4). At the end of the feeding period, biometric parameters, textural properties of muscle, as well as protein, lipid and collagen contents, and electrophoretic protein profiles of this tissue were studied. The decrease in dietary protein content improved textural parameters (increased firmness and water holding capacity). Within each dietary protein level, diets with high carbohydrate and low lipid contents resulted in lower values of muscle firmness than diets with low carbohydrate and high lipid contents. This increase in firmness matched with a lower muscle lipid and higher muscle collagen contents. SDS-PAGE separation of muscle extracts showed a higher relative contribution of myosin to total optical density in muscle from those animals fed lower dietary protein, although no significant difference in fish texture could be attributable to this finding. Results indicate a favourable effect of replacing protein by alternative energy sources (lipids or carbohydrates) on the rheological properties of muscle in this species, this improvement was more noticeable when protein was replaced by lipid than by carbohydrate.

Periploca laevigata is an abundant and palatable tannin-containing shrub present in the south-east coastal area of Spain. Sheep and goats usually consume this species, which represents 7·2% of total dry matter (DM) intake per year. Periploca laevigata is an important grazing species in the dry season, despite its high tannin content. The objective of the present work was to examine the tannin level of P. laevigata in relation to the extent of utilization by small ruminants, as well as in response to simulated browsing. Periploca sprouts were collected in three areas from plants exhibiting either medium (0·51 animals/HA), low (0·34 animals/HA) or no (0 animals/HA) browsing by small ruminants. These sprouts were also collected in plants with simulated herbivory twice (in two successive months), once, and with no simulated herbivory. A greater concentration of tannins (p

This study evaluates the in vitro protein hydrolysis of four microalgae (Tisochrysis lutea, Nannochloropsis gaditana, Tetraselmis suecica and Scenedesmus almeriensis) by intestinal proteases of gilthead sea bream (Sparus aurata) and Senegalese sole (Solea senegalensis). The hydrolysis of protein was monitored at different sampling times by electrophoretic techniques, and the quantification of the free amino acids released by proteases. Overall, S. aurata or S. senegalensis proteases hydrolysed microalgae protein in a similar way. The highest hydrolysis values (coefficient of protein degradation, CPD > 70%) were obtained for Tisochrysis and Nannochloropsis biomasses, which showed a progressive and almost complete proteolysis at the end of the in vitro assay. Tetraselmis and Scenedesmus protein was also hydrolysed, but SDS-PAGE revealed that two protein fractions remained virtually intact at the end of the in vitro assay. The final amount of free amino acids released in vitro by the fish digestive enzymes ranged from 9 to 25 g 100 g protein−1. A linear relationship between CPD and the amount of free amino acids released was found, a fact that suggests that microalgae protein is hydrolysed efficiently by the digestive proteases of both fish species. The present study provides information about the protein availability from selected microalgae, which will aid in the initial evaluation of the microalgae as potential protein sources in feeds of two important farmed fish species.